1. Field of the Invention
This invention relates to a catheter systems with an insertion wire and a catheter. More specifically, this invention relates to such catheter systems in which at a distal end of the catheter at a tip, there is provided an insertion wire lumen which extends from the tip to an opening provided laterally in the catheter.
2. Description of the Prior Art
Placement of catheters through small blood vessels is currently done essentially by means of a technology combining two different processes. In the standard process, the radial artery is used to monitor the arterial blood pressure and the arterial blood gases, especially in the perioperative area under anesthesia. Generally, in this standard process, a single-lumen intravasal catheter of teflon or of polyurethane with a length between 3 cm and 5 cm and with a diameter up to 18 gauge are inserted into the radial artery. Catheters are inserted conventionally via a guide cannula which fills the lumen of the catheter and projects above it. In addition, the arterial pressure is generally measured invasively by means of a liquid coupling to an external pressure transducer. Blood gases and other physiological parameters are determined from blood samples which are collected through the catheter lumen.
One disadvantage of the existing technique of puncturing the radial artery and inserting the above described catheter into the vascular lumen is that the catheter cause a reactive constriction of the radial artery and thus, interruption of the blood flow on the catheter often occurs. This, in turn, results in incorrect pressure measurements which is described by R. Mohr, J. Lavee and D. A. Goor in xe2x80x9cInaccuracy Of Radial Artery Pressure Measurement After Cardiac Operationsxe2x80x9d published in the J. Thorac. Cardiovascular Surg. 94(2), 286-290 (1987). This pressure measurement is erroneously interpreted as being accurate while in fact, the pressure measurement is inaccurate because it is acquired by measuring a pulsating stagnating blood column.
If blood is taken via the pressure/blood collection lumen of the catheter, the biochemical or physiological values of the sample often do not agree with the actual values since this blood originates, at least in part, from a blood column which is not being circulated. Analogous inaccurate measurements arise when a relatively short radial catheter is provided with sensors for measuring biochemical or physiological parameters such as blood gases.
In addition, central arterial pressure curves is necessary in critical situations. However, pressure curves in the radial artery generally deviate dramatically from pressure curves measured in central arteries such as the aorta, both in the shape of the pressure curve, and in systolic and diastolic blood pressures. This deviation is discussed by G. P. Gravlee, S. D. Brauer, M. F. O""Rourke, and A. P. Avolio in xe2x80x9cA Comparison Of Brachial, Femoral And Aortic Intra-Arterial Pressures Before And After Cardiopulmonary Bypassxe2x80x9d published in Anaesth. Intensive Care, 17(3), 305-311 (1989).
Peripheral-arterial pressure curves from the radial artery are also not suitable for computing the cardiac output using the pulse contour method because an unambiguous diagnosis of the ejection phase of the left ventricle is not possible. Centrally measured pressure curves are required for this purpose. This is discussed by K. H. Wesseling, B. de Wit, A. P. Weber, N. Ty Smith in xe2x80x9cA Simple Device For The Continuous Measurement Of Cardiac Outputxe2x80x9d published in Adv. Cardiovasc. Phys., vol 5 (Part II); 16-52 (1983).
The cardiac output and circulatory filling state in the perioperative area are generally determined through a pulmonary-arterial thermodilution catheter placed within the radial artery in addition to the arterial radial catheter. In the surgical arts, the pulmonary-arterial thermodilution catheter is also known as a pulmonary catheter or a pulmonary arterial catheter. In pulmonary arterial thermodilution, a glucose or saline solution which has a temperature which deviates from the blood temperature is venously injected. The pulmonary arterial catheter placed in the pulmonary artery includes a temperature sensor on the distal end which allows recording of the thermodilution curve. For example, the cardiac output is computed from the thermodilution curve by means of the Stewart-Hamilton process. Furthermore, by inflating a balloon placed on the distal end of the catheter, a pulmonary arterial closing pressure is recorded which will provide information on the circulatory fill status.
The cardiac output and the circulatory fill status can also be measured by means of transcardiopulmonary arterially measured thermodilution as discussed in U.S. Pat. No. 5,526,817 to U. J. Pfeiffer and R. Knoll or also by means of thermo-dye dilution as discussed by U. J. Pfeiffer, G. Backus, G. Bluemel, J. Eckart, P. Mueller, P. Winkler, J. Zeravik, and G. J. Zimmerman in xe2x80x9cA Fiberoptics-Based System For Integrated Monitoring Of Cardiac Output, Intrathoracic Blood Volume, Extravascular Lung Water, O2 Saturation, And a-v Differences, Practical Applications Of Fiberoptics In Critical Care Monitoringxe2x80x9d published in Springer Verlag, p. 114-125 (1990). However, existing measurement catheters allow simple and reliable measurements in the femoral artery and in the abdominal aorta.
Experience shows that the currently available arterial thermodilution and thermo-dye dilution catheters with a blood pressure lumen having an extremely small diameter of 1.33 mm still do not allow reliable thermo- or thermo-dye dilution measurements in the radial artery because they can only be placed into position by an insertion catheter with a much larger outside diameter. However, measurement through the radial artery is necessary during anesthesia because during many surgeries, the anesthetist does not have any opportunity to correct the location of the femoral catheter. In addition, such measurements may also be required if as a result of the completed surgery, there is no blood flow in the femoral artery or the blood flow it is influenced by the surgeon.
The disadvantages of the existing arterial thermo- or oximetry/thermo-dye dilution catheters include the fact that the sensors such as a fiber optic eye or a thermistor have been attached to the distal end and end flat on the catheter end next to the opening of the blood pressure lumen. In addition to the insertion of the measurement catheter, this requires the use of an additional insertion catheter which pushes the measurement catheter into the blood vessel. Consequently this system results in a much larger puncture surface and thus, can cause damage to the blood vessel wall and reduce blood flow because of the greater diameter.
Furthermore, the fiber optic eye which is often unprotected on the tip of the catheter, is frequently blinded since the catheter tips adjoin certain structures of the vessel wall such as branches, atherosclerotic changes, etc. and its function can be adversely effected because of formation of a microthrombus.
The German reference DE 42 00 032 C2 discloses a catheter system in which a catheter is preferably provided with a dilation balloon, by means of which constricted vessels, for example coronary vessels, can be widened. A catheter of this type is usually inserted via a lock attached to the femoral artery of the patient, and is pushed into the coronary system via the patient""s aorta as disclosed in the German reference DE 42 00 030 C2. In this manner, the catheter is guided by the guide wire in the area of the catheter tip whereas in the proximal catheter area adjacent to the catheter tip, it is guided by the parallel guide wire lying outside the catheter but within the blood vessel.
The guide wire is thus used in the catheter system known from DE 2 00 030 C2, to guide the catheter tip within the blood vessel system. Due to the necessity of using an insertion catheter or a lock, the insertion of this catheter requires a comparatively large puncture surface. Due to the long length of the guide wire (which usually has at least the length of the catheter, but generally have twice the length of the catheter), a large sterile surgical field is necessary since the guide wire can easily come into contact with articles in the vicinity of the patient during its insertion.
The published European Patent ApplicationEP 0 266 928 A1 discloses a multifunction cardiovascular catheter system but fails to disclose the use of a guide wire or insertion wire.
In view of the foregoing, it is an object of the present invention to provide a catheter system that can be quickly and easily placed in small blood vessels, for example in the radial artery, by means of direct insertion wire technique with little traumatizing effect.
A second object of the present invention is to provide a catheter system which can ensure that the sensor or the sensors on or in the catheter comes to rest in an area of the vessels in which blood flows past the catheter and in an area in which the shape of the blood pressure curve closely corresponds to that in the aorta when placed in the arterial system.
Another object of the present invention is to provide a catheter system with a relatively short insertion wire in order to make the sterile covering as small as possible when the blood vessel is punctured.
Yet, still another object of the present invention is to provide a catheter system wherein the catheter remains positionable and repositionable under sterile conditions.
With the catheter system in accordance with the present invention, it becomes possible to push the catheter into the vicinity of the aorta, for example via a minimally traumatizing puncture of the radial artery, in order to take measurements, like blood pressure measurements or optical spectral measurements, which are far superior than previous measurements possible through a puncture of the radial artery.
The improved catheter system in accordance with the present invention is used in the manner described below. The radial artery is punctured in the conventional manner by means of a cannula. Then, the short insertion wire is pushed via the lumen of the cannula into the blood vessel and the cannula is withdrawn while holding the insertion wire stationary. The puncture side of the blood vessel is widened by a dilator. Then, the dilator is likewise withdrawn, leaving the insertion wire in the vessel. The insertion wire is then threaded into the distal opening in the tip and the catheter is pushed forward. The insertion wire is pushed forward far enough to allow the insertion wire to project out of the first opening on a surface of the catheter so that it can be securely gripped by the surgeon with his or her fingers. Then, by using the insertion wire, the catheter is pushed roughly 5 cm through the skin and the subcutaneous tissue into the blood vessel. Then the insertion wire is pulled. Subsequently, the catheter (without the insertion wire) is pushed forward approximately another 50 cm so that its tip reaches a large artery (for example, the axillary artery). The attachment of the catheter is minimally traumatizing since only the easily accessible radial artery need be punctured and the use of a lock is not necessary. Because the insertion wire is short, the sterile field can be kept very small without the danger of contamination of the insertion wire during the insertion.
In contrast to the teachings of the prior art German reference DE 42 00 030 C2, the short insertion wire provided in the present invention is not used to guide the catheter within the blood vessel system, but rather to insert the catheter through the puncture site into the blood vessel system. Therefore, in contrast to the German reference DE 42 00 030 C2, the short insertion wire provided in the present invention replaces the lock or insertion cannula usually necessary for insertion of catheters. Thus, the present catheter system is substantially different than that disclosed in the German reference DE 42 00 030 C2 and fulfills a completely different purpose. More specifically, the guide wire as disclosed in DE 42 00 030 C2 has a length which is at least equal to the length of the catheter since it is used to insert the catheter along with the guide wire into small blood vessels, for example into the coronary system.
These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the intention when viewed in conjunction with the accompanying drawings.